I thought all of the MSP430 family could implement a semi hardware/software UART using Timer "A"? In fact, this (apparently) is how the bootstrap loader gets its serial info, even in the 149.
I would seriously consider the even later 16x family though, it has several channels of DMA, which might end up being very convenient! (As well as having two UARTS, and some extra modes!) Furthermore, careful study of the datasheet shows that to GUARANTEE operation of the 13x/14x family at 8 MHz, you need to have a Vcc of at least 3.6 volts. (Although, I have not had any issues running at 3.3 volts / 8 MHz, but have not tested at elevated temperatures.) The 13x/14x (and the later family as well) also have a "modulation" register which allows for fine tuning of the baud rate register, so you can get reasonably close to nearly any baud rate required, virtually independently of the crystal used. (But, it is easier to run at a multiple of the baud rate!) As suggested in another reply, you don't have a lot of time up your sleeve. 115200 will give you a character every 87uS (roughly) ( a bit time is 8.7 uS) so with an MSP @ 8 MHz, you might get (roughly) 150..400 instructions between characters, will that be enough to do your conversion? (Also as suggested, the best approach is over sampling at the bit rate, you would be lucky to get 50 instructions at the bit rate! without oversampling) The smaller MSPs do not have a huge amount of SRAM on board either, so will they have enough to buffer a full packet? (And then do the conversion.) (No compensation made for interrupt latency time either, which strips (approx) a couple of uS from the inter char time as well! However, you could potentially write the software for the device you suggested, and then check the timing, (some of the produce-able listings show a cycle count, but off hand, I cannot remember which) if it doesn't come close after optimisation, the code would still be OK to modify for the better device in the family. In the end, it really comes down to price though. A $1.5 versus a $7 price point. Can the project support the higher price, which ends up being trivial in the scheme of things? Cheers Harry [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Pedro Zorzenon Neto Sent: Tuesday, November 19, 2002 11:32 PM To: mspgcc list Subject: [Mspgcc-users] msp uart emulation by software Hi Folks, I don't think this is the best place to post this question, but I think you can answer that :-) I need to build an "serial protocol converter" and I intend to use MSP430. The hardware should read data from serial0, convert it and write to serial1. Also read data from serial1, convert it and write to serial0. Also need one I/O to blink a Led when there is data being processed. Do you think that I can use msp430f123 that has only one UART and emulate the other UART by software? (both uarts will work at 115200 8N1, msp will run at 8MHz) I know this is not an easy question... just want some hints... Has anyone emulated UART by software? Thanks, Pedro ------------------------------------------------------- This sf.net email is sponsored by: To learn the basics of securing your web site with SSL, click here to get a FREE TRIAL of a Thawte Server Certificate: http://www.gothawte.com/rd524.html _______________________________________________ Mspgcc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/mspgcc-users
